1. Field of the Invention
Exemplary embodiments of the present invention relate to a lens for light emitting diodes (LEDs) and, more particularly, to an aspherical LED lens and a light emitting device including the same.
2. Discussion of the Background
A LED refers to a semiconductor device that has a p-n junction and emits light upon recombination of electrons and holes in the p-n junction based on a potential difference formed therein. An LED may be composed of compound semiconductors such as GaN, GaAs, GaP, GaAs1-xPx, Ga1-xAlxAs, InP, In1-xGaxP, etc., and has generally been used for display lamps or devices for displaying simple information such as numerals. In recent years, with the development of technologies such as information display technology and semiconductor technology, LEDs may be used not only for flat panel displays such as liquid crystal display devices, but also for general lighting.
LEDs may have advantages, such as superior energy efficiency to and longer lifespan than existing light sources, no discharge of harmful ultraviolet (UV) light, and environmental friendliness, and are thus increasingly a focus of attention as a light source that can replace existing cold cathode fluorescent lamps (CCFL).
However, when LEDs are applied to a light source for a backlight unit of a display device, a panel disposed directly on the LEDs may have high illumination but a region between the LEDs may have low illumination due to point light source characteristics of the LEDs, whereby the entirety of the panel may have uneven illumination. Further, when the LEDs are applied to a street lamp, for example, only a region directly below the street lamp may be bright, and a road surface between street lamps may be dark, causing pedestrian or driver inconvenience.
Specifically, a conventional LED will be described herein with reference to an example wherein a semispherical LED lens is employed as a light source for a backlight unit.
FIG. 1 is a side sectional view of a light emitting device 100 including a conventional semispherical LED lens, FIG. 2 is a graph depicting an orientation angle curve of is light emitted from the light emitting device 100, and FIG. 3 is a graph depicting illumination on a panel of a display device according to arrangement of the light emitting devices 100 when the light emitting devices 100 are used as a light source for the backlight unit.
As shown in FIG. 1, the conventional light emitting device 100 includes an LED chip 2 and a semispherical LED lens 4 which adjust an angle of light emitted from the LED chip 2. Although not shown in the drawings, the light emitting device 100 may further include a fluorescent material deposited on the LED chip 2 to generate white light.
Referring to FIG. 2, since light emitted from the light emitting device 100 as shown in FIG. 1 is focused on the center of the lens 4 due to the semispherical structure of the lens 4, the light may have a symmetrical pattern of orientation angles such that illumination increases towards a central axis of the lens and gradually decreases towards right and left sides thereof.
Accordingly, as shown in FIG. 3, when the light emitting devices 100 including the semispherical LED lenses are linearly arranged in the backlight unit of the display device, illumination on a panel above the light emitting devices 100 may be uneven, and bright and dark areas may be repeatedly formed on the panel.